1. Field of the Invention
The present invention relates to flame resistant fiber reinforced thermoplastic composites, and more particularly relates to flame resistant thermoplastic composites having reinforcing glass fibers and a heat-expandable material.
2. Description of the Related Art
Thermoplastic composites having reinforcing materials and aqueous methods for making such fiber reinforced composite materials from an aqueous slurry of solid polymer and reinforcing material are known, see Published European Patent Applications 0,148,760 and 0,148,761, Wessling et al., U.S. Pat. No. 4,426,470 issued Jan. 17, 1984, and Gatward et al., U.S. Pat. No. 3,716,449 issued Feb. 13, 1973, all of which are incorporated herein by reference. In general these reinforced polymer composites have a uniform mixture of fiber, polymer and optionally binder and are prepared by performing dilute aqueous slurries of a solid heat-fusible organic polymer, a reinforcing material and optionally a latex binder.
Reinforcing materials disclosed have included organic and inorganic products such as graphite, metal fibers, aromatic polyamides, cellulose and polyolefin fibers, and typically have included glass fibers such as chopped glass strands having a length of 1/8 to 1 inch (about 3.2 to 25.4 mm) or milled glass fibers which generally have a length of about 1/32 to 1/8 inch (about 0.79 to 3.2 mm). While these composites which are prepared by the above described method exhibit levels of flame resistance as measured by OSU performance tests for heat release and smoke release, there is a continuing desire to improve the flame resistance performance of such composites.